Background: Colorectal cancer is a major health problem worldwide and many efforts have been done to delineate risk factors and develop screening strategies to reduce its incidence and mortality. Colorectal adenomas have been clearly considered preneoplastic lesions due to their potential malignant transformation via the adenoma-carcinoma sequence. Over the last years, intestinal microbiota has been studied in several diseases and it has been hypothesized that colonic microbiota could influence colorectal cancer pathogenesisObjective: The goal of this study is to analyse whether there is an association between the fecal microbiota profiling and the presence and progression of colorectal adenomas, detected in population undergoing colonoscopy, to better understand the role of intestinal microbiota in colorectal carcinogenesisDesign: A cross-sectional study in the Gastroenterology Department at Hospital Universitari Doctor Josep Trueta in Girona, in a period of time of two yearsParticipants: General population undergoing screening or diagnostic colonoscopy in the Digestive Endoscopy UnitOutcomes: Identification and characterization of intestinal microbiota in stool samples from healthy patients and patients with low and high risk colorectal adenomas